1. Field of the Invention
The present invention relates to an instrument for examining the fundus of the eye, and more particularly to an improved stereo ophthalmoscope or microscope for examining the fundus of the eye and for presenting an upright and unreversed image of the retina to the observer.
2. Description of the Prior Art
When the fundus of the eye is subject to examination and ophthalmic surgery, it is of advantage that the magnified image be as faithful as possible to the object. In the past, with indirect ophthalmoscopy, the fundus was viewed as an inverted reversed image since conventional optical systems were used.
Attempts have been made to provide upright and unreversed imagery in fundus ophthalmoscopes. One such ophthalmoscope includes a single objective lens, a separating prism spaced from the object lens separating the image rays into two groups and passing the rays to separate reflecting and laterally correcting prisms and then through an erecting lens system for each eye. This ophthalmoscope achieves the desired result, but the accuracy at which prisms and lenses must be placed in the housing and the overall length thereof makes it less practical.